The development of feeding and drinking behavior will be studied in the suckling rat with techniques that 1) allow for the measurement of both its milk and water intake, and 2) permit the injection of chemical agents into its brain in a benign procedure that does not interfere with its subsequent behavior. We will continue to study the ontogenetic calendar with which the developing brain becomes responsive to agents that arouse (renin, angiotensin, hypersomotic solutes) or suppress drinking (prostaglandin Es), and that arouse feeding (norepinephrine, 2-deoxy-D-glucose). Having found two treatments that induce hyperphagia in the newborn (1) complete subdiaphragmatic denervation, + (2) removal of a preweanling rat from the litter for free-feeding through an oral catheter, we will investigate the mechanism of both and their implications for control of suckling and adult feeding. We will study the effects of early nutritional history on adult drinking behavior. Weanling rats will be raised on dilute liquid diet or will be desalivated. Both regimes will prevent body water losses, but one (the former) will provide excess oral lubrication, and the other will dry the mouth. The temporal pattern of the animals' spontaneous meals and drafts and their responsiveness to deficit signals will be studied when normal oral conditions are restored and when the animals are challenged with deficits in adulthood.